Lewis structures ionic

Examine electrostatic potential maps for potassium hydride and hydrogen chloride. How are they similar and how are they different (Focus on whether the molecules are polar or nonpolar (compare dipole moments), and on the electronic character of hydrogen.) Draw the ionic Lewis structure that is most consistent with each electrostatic potential map. Does each atom have a filled valence shell ... 

EXAMPLE 10.2 Writing Ionic Lewis Structures Write the Lewis structure of the compound MgO. ... 

In an ionic Lewis structure, the metal loses all of its valence electrons to the nonmetal, which attains an octet. The nonmetal, with its octet, is normally written in brackets with the charge in the upper right comer. 

Determine what is wrong with each ionic Lewis structure and write the correct structure. 44. Determine what is wrong with each ionic Lewis structure and write the correct structure. 

Each compoimd listed contains both ionic and covalent bonds. Write the ionic Lewis structure for each one, including the covalent structure for the polyatomic ion. Write resonance structures if necessary. 

The melting point of ionic solids depends on the magnitude of the electrostatic attractions that hold the solid together. Draw ionic Lewis structures for NaF and MgO. Which do you think has the higher melting point ... 

Draw ionic Lewis structures for KF and CaO. Use the information and the method in the previous problem to predict which of these two ionic solids has the higher melting point. 

The weights of the two Kekule structures account for 19.5 % and those of the 12 ionic Lewis structures with adjacent charges for 20 %. See text for explanation... 

In an ionic Lewis structure involving main-group metals, the metal transfers its valence electrons (dots) to the nonmetal. 

All the following compounds are charactenzed by ionic bonding between a group I metal cation and a tetrahedral anion Wnte an appropriate Lewis structure for each anion remembenng to specify formal charges where they exist... 

The four structures with three double bonds (third row) and the one with four double bonds are the most plausible Lewis structures, (b) The structure with four double bonds fits these observations best, (c) +7 the structure with all single bonds fits this criterion best, (d) Approaches (a) and (b) are consistent but approach (c) is not. This result is reasonable because oxidation numbers are assigned by assuming ionic bonding. 2.109 The alkyne group has the stiffer C—H bond because a large force constant, k, results in a higher-frequency absorption. 

There are also molecules that are exceptions to the octet rule because one of the atoms has fewer, rather than more than, eight electrons in its valence shell in the Lewis structure (Figure 1.19). These molecules are formed by the elements on the left-hand side of the periodic table that have only one, two, or three electrons in their valence shells and cannot therefore attain an octet by using each of their electrons to form a covalent bond. The molecules LiF, BeCl2, BF3, and AIC13 would be examples. However, as we have seen and as we will discuss in detail in Chapters 8 and 9, these molecules are predominately ionic. In terms of a fully ionic model, each atom has a completed shell, and the anions obey the octet rule. Only if they are regarded as covalent can they be considered to be exceptions to the octet rule. Covalent descriptions of the bonding in BF3 and related molecules have therefore... 

Lewis considered covalent and ionic bonds to be two extremes of the same general type of bond in which an electron pair is shared between two atoms contributing to the valence shell of both the bonded atoms. In other words, in writing his structures Lewis took no account of the polarity of bonds. As we will see much of the subsequent controversy concerning hypervalent molecules has arisen because of attempts to describe polar bonds in terms of Lewis structures. 

Ca— 0 is improperly written as a covalent Lewis structure, although CaO is an ionic compound. In addition, there are only two electrons around the Ca atom. [Ca]2+[ 0 ]2" is a more plausible Lewis structure for CaO. 

In practice, the NBO program labels an electron pair as a lone pair (LP) on center B whenever cb 2 > 0.95, i.e., when more than 95% of the electron density is concentrated on B, with only a weak (<5%) delocalization tail on A. Although this numerical threshold produces an apparent discontinuity in program output for the best single NBO Lewis structure, the multi-resonance NRT description depicts smooth variations of bond order from uF(lon) = 1 (pure ionic one-center) to bu 10n) = 0 (covalent two-center). This properly reflects the fact that the ionic-covalent transition is physically a smooth, continuous variation of electron-density distribution, rather than abrupt hopping from one distinct bond type to another. 

Table 3.1 compares key bonding and ionicity descriptors for the NBO Lewis-structure representations of the five AF diatomic fluorides in this series. From this table it can be seen that the single-term natural Lewis-structure description is practically exact for all species (with %p 99.9% for A = F, Cl, Br, H, and only a... 

A third, more extreme, conceptual model, based on a completely ionic picture of hypervalent bonding, can also be invoked to remove perceived conflicts with Lewis-structural principles. In PF5, for example, the completely ionic ( oxidation number ) P5+(F )5 representation... 

Figure 2.14 Lewis structure of ionic sodium chloride. Note how the outer shell of the sodium ion is empty, so the next (inner) shell is full...

---